In a known, computer-supported control system, which is described in the U.S. patent application Ser. No. 4,787,049 (Hirata at al), a personal computer is provided which, in usual fashion, comprises a microprocessor, a ROM, a read-write memory, and a disk memory. Furthermore, as is generally usual, the personal computer comprises a monitor and a keyboard. The individual components of the personal computer are connected via interface circuits to an internal PC bus of the personal computer. On the output side, the personal computer is connected to a sequence controller via an interface circuit that is connected to the PC bus. The abbreviation "PC" throughout the specification means "personal computer". The sequence controller tool or to drive a numerical control unit, which Is connected to the axis drivers of a machine tool via driver units. The known control system therefore essentially Involves two separate units, namely the personal computer on the one hand and the CNC on the other hand, which are connected together by a control, which can essentially be regarded as a serial interface. Such a control system on the one hand is comparatively slow due to the high data density which must be transmitted between the personal computer and the CNC via the sequence controller and, on the other hand, is suited only to drive a single CNC and a single machine tool.
From the technical publication ISIS Engineering Report 1987, 5th year, Volume 1, April-October, Pages 3002-3005, a control system is known, with a personal computer which comprises a PC bus, and with a CNC that is connected to the PC directly via a parallel port. The CNC on its part is connected, via another parallel port, to a machine-tool driver-circuit, designated by "SPS". Every transmission of data from the PC to the control runs through the CNC and loads the latter. Thus this system ia not suited to work with more than a single CNC.